Note: The following is an abridged version of the American Philatelist article. Click here to read the full article, as well as see previous issues of the American Philatelist. Wayne Yougnblood is also presenting a course about stamp technology for the 2022 Summer Seminar , and has taught multiple courses on the C3a learning platform.
Virtually all collectors know the words “line engraving,” “offset,” “gravure” and other printing terms, but that’s frequently where the understanding of how stamps are printed ends. Yet, a reasonable understanding of how stamps are printed and – more importantly – how to tell them apart, is an extremely vital part of stamp identification, as well as developing the ability to weed out fakes, forgeries and alterations.
Although there have been dozens of books and hundreds of articles focused on stamp production over the years (most notably, Fundamentals of Philately by L.N. and M. Williams), there are some basics that almost cannot be covered frequently enough. Stamp printing is one of them.
The following will be a quick survey of all four major types of stamp printing, as well as brief descriptions of a few others. Hopefully, between the descriptions, characteristic information and images, you will have little difficulty determining methods of printing on your own stamps. I’ve found it a refreshing learning activity to sometimes sit down with a pile of foreign stamps and simply examine and identify the printing types. For many modern stamps, more than one printing type may be used on a single stamp.
Preliminaries
Before going further, it is essential to note that although there are many different ways to place ink on paper, there are basically only two forms of printing: direct and indirect.
Figure 1. Direct printing, as shown here by both flat plate and rotary press, involves direct contact between the printing base (plate) and the substrate (paper).
Direct printing (Figure 1) refers to the application of ink by direct contact between printing surface and substrate (paper, plastic or whatever you’re printing stamps on). Indirect (or offset) (Figure 2) involves having an additional surface (such as a rubber blanket) that receives the ink from the plate and deposits it on the substrate.
Figure 2. Indirect printing (offset) involves adding another surface to the printing process, such as a roller, which receives the inked impression from the plate or sleeve and deposits it on the paper. Although the offset process is most commonly used with lithography, it can be used with any of the printing types described (although it’s rarely been done with gravure).
Thus, virtually any of the methods of printing we discuss may be applied either directly or indirectly, although it makes little sense to do one or the other with some printing types. More on this in a bit.
You’ll find many images of stamps and enlargements of details throughout this article that illustrate the different aspects of each printing type. You’ll also see the same dummy stamp design produced by each type of printing to clearly illustrate the differences between each. These items were created for An Introduction to Advanced Philately, by A.J. Sefi, published in two limited editions (1926 and 1932), which is a treasure trove of information.
Methods and Processes
Figure 3. Diagram of the major printing types used to print stamps and how this is accomplished.
The following are the major printing types found on stamps, followed in parentheses by other terms that are frequently used to describe them (Figure 3):
- Line-engraved intaglio (copperplate, etching, die stamping, plate printing)
- Gravure (screen intaglio, photogravure, rotogravure, heliogravure)
- Letterpress (typography [obsolete term], photoengraving, flexography, letterset/dry offset, high-etch, rubberstamp)
- Lithography (stone litho, dilitho, planography, collotype)
The following are additional forms of “printing” that have been used for producing stamps. Not all are true printing types, as they describe characteristics or inks.
- Thermography
- Microprinting
- Stencil, including mechanical, mimeograph, silk screen, serigraphy, screen printing and more)
- Reflection (most photocopying machines)
- Ink jet (actuated by punched cards, disk, punched or magnetic tape)
These will be very briefly discussed later.
Line Engraving (Recess Printing)
Figure 4. Line-engraved intaglio is noted for its fine detail and three-dimensional qualities, as well as its almost certain protection against counterfeiting.
Without exception, line-engraved intaglio printing is considered the finest, most attractive and secure form of printing stamps because it’s virtually impossible to accurately counterfeit an engraving line by line (Figure 4).
Even with modern printing technology, a reproduction of an engraved stamp is easy to spot; it simply does not have the same depth of appearance. Further, engraving offers an unsurpassed, three-dimensional potential for design purposes. The art of the original engraver is quite evident in the final product, with little loss in translation.
Figure 5. Original master die (now corroded) engraved for the 1930 APS convention seals. As you can see, the design appears reversed. The darkened lines are recessed below the surface of the die.
As a form of recess printing, line engraving utilizes incised areas on a printing plate (or base) that hold ink (Figure 5) and, when (usually) moistened paper is pressed against it under intense pressure, the ink is pulled from the recesses. The ink is slightly raised above the surface of the paper and can be felt in some cases. This also helps give a more three-dimensional appearance to the finished work.
Figure 6. Master die for engraving of Walt Whitman, courtesy Library of Congress.
Figure 7. Detail of fine line work in the Whitman engraving.
Figure 8. France Scott B400, issued in 1966, shows an engraver’s hands working on a master die – albeit at a very awkward angle.
For postage stamps, line engraving begins with a master die (Figure 6) of softened steel (untempered), although copper also can be used for small press runs. Details of the design (Figure 7) are frequently transferred to the die with the use of special transfer wax, beeswax, to serve as a guide for the engraver. Once this is done, the engraver begins work using a graver, or burin, to essentially carve into the die (Figure 8).
Figure 9. A Bureau of Engraving and Printing engraver is shown working on the master die for the 1¢ Alexander Graham Bell stamp of the 1940 Famous Americans series.
The design is engraved in reverse, usually by hand, alhough pressure transfer and machine types are occasionally used (Figure 9). Typically, there are specialized artists used for the frame, lettering and the portrait or other central subject. The width and depth of these incised markings help to give the finished engraving much more of an appearance of depth. Due to the nature of engraving, the design is made up entirely of lines (hatching), cross-hatching and stippling. Large, solid areas cannot be used, as the ink in them would be lost during the wiping process.
Figure 10. The completed transfer roll for the 1930 APS convention show label. The design is forward reading and stands out from the roll in relief.
After the die is finished and approved, it is hardened (tempered) and one or more transfers are taken up on the periphery of a softened steel roll known as a transfer roll (Figure 10). As the transfer roll is being rocked over the hardened die, metal from the roll molds into the incised areas, creating a raised image. These transfers are the reverse of the die (forward reading). Instead of being incised, the designs stand out and are known as “reliefs.”
Figure 11. The siderographer works on transferring images from the transfer roll to a printing plate.
The transfer roll is then hardened (tempered) and used to transfer the design into a softened (untempered) steel plate up to the desired number of subjects (Figure 11). Now that the transfer roll is hardened, it displaces metal in the printing plate, created reverse-reading recessed areas.
Figure 12. Completed die proof of the engraved Sefi dummy stamp design.
Once finished, a proof is taken for approval and any necessary cleanup or corrective work is performed (Figure 12).
Figure 13. This is the completed printing plate (12 subjects) for the 1930 APS convention label.
Depending on the kind of press to be used, the plate is then curved or left flat, hardened, and usually chrome plated. Chrome plating of postage stamp plates began at the Bureau of Engraving and Printing in 1927. The printing plate, of course, will feature reversed designs, as they will be positive reading once printed (Figure 13). Once the plate, sleeve or cylinder is mounted on the press, ink is applied, wiped (leaving ink only in the incised areas and applied to the substrate (usually paper) under pressure.With some changes in handling due to equipment or other techniques being used, this more or less describes the line engraving method as originally developed by Jacob Perkins in the early 1800s. In the beginning, plates were not always hardened, and they were never curved. All printing was flat-plate printing. Rotary presses, with curved plates, were an advent of the 20th century.
Figure 14. Modern curved-surface siderography at the Bureau of Engraving and Printing (cropped).
Figure 15. The publicity image of this 1980 Swiss stamp shows a closeup of transferring an image from a curved transfer roll to a printing sleeve.
A 1975 U.S. development in siderography (the practice of transferring images from die to plate) is to transfer designs from a roll directly to a cylinder, or sleeve, instead of transferring them to a flat plate and bending it for rotary press use (Figures 14, 15). The first stamp issued from this type of transfer process was part of the printing for Scott 1625, the 13¢ Flag Over Independence Hall stamp.
Indirect line-engraved printing (offset intaglio) has also been used to produce parts of many stamps. The U.S. Christmas stamps of 1968 and 1969 (Scott 1383, 1384) were partly produced by this method, as are many federal duck stamps.
Figure 16. The honeybee on this stamp (enlarged from the 1988 coil issue) stands out clearly in relief from the paper it was printed on (the background image was produced by offset lithography). Note the lines of detail.
Figure 17. This stamp from Peru shows the fine linework found on most engraved stamps.
Figure 18. All design elements on engraved stamps are made up of lines, such as found on these two stamps.
How to Identify Line Engraving (Figures 16, 17, 18)
- Engraved stamps normally have a sharp, crisp appearance, with strong rich tones.
- All design elements are made up of lines and stippling (small dots); no large solid areas are present.
- There is often a raised feel to the print which can also be seen under magnification and oblique lighting (use 5X glass or stronger).
- Debossing is sometimes visible on the reverse side.
Selected ‘Pseudo’ Printing Types
Thermography
There are two types of printing that are referred to by this term. Both rely on heat to create images.
Figure 37. At first glance this stamp looks like it could have been printed by line engraving – and the ink is raised – but a closer examination (photographed here under oblique light), reveals the raised imaged of thermographic ink, or “poor man’s engraving.”
The first and most recognizable (Figure 37) is what is often called “poor man’s engraving.” All printed areas are raised – usually much more so than line engraving. This effect is caused by using a resin-based ink, usually applied either by letterpress or lithography, that is heated, causing the resin to expand.
Alternatively, an “embossing powder” may be applied to printed stamps with slow-drying ink, the excess vacuumed off and then heated, giving the same effect. Stamps printed by thermography (of which there are very few) are easily distinguished from engraved stamps by their cruder appearance and softer lines.
Figure 38. The U.S. Autopost experiment created stamps printed on heat-sensitive, or thermographic, paper.
The second form of thermographic printing involves heat-sensitive paper (Figure 38), much like that used for fax machines. One of the more notable of these stamp issues is the 1989 U.S. Autopost experiment.
Microprinting
Figure 39. This 1954 issue from Greece (Scott 571) is one of the earliest to incorporate microprinting in its design.
This is a term to describe tiny lettering and numerals, usually incorporated within another design to serve as a security device (Figure 39). What distinguishes microprinting is the fact that one generally needs to use magnification to read it. While there have been instances of line-engraved microprinting, more often than not it is applied by offset lithography.
Reflection
This is the type of printing technology used by most photocopying machines, utilizing toner. U.S. Postal Buddy postal cards were created in this manner.
Ink jet
Figure 40. Most Frama stamps, such as this one from Finland, were printed on some form of security paper by an inkjet process. The spray pattern is visible in the numerals.
Again, infrequently used for postage stamps, but found on many Frama-type stamps from different countries (Figure 40). Inkjet is a form of computer-generated printing that recreates an image, numeral or letter by spraying droplets of ink onto the substrate. Modern “netstamps” and computer-generated postage frequently utilize inkjet printing.
Author’s Note: I’d like to take a moment to acknowledge the late George Brett, who was not only the penultimate gentleman, but who took me under his wing more than 30 years ago and added an accelerant to my interest in printing technology, allowing it to burn uncontrollably ever since.